Our overall objective is to define the physiological and biochemical bases for the release of lysosomal protein into bile. We are exploring the hypothesis that exocytosis of lysosomal contents into biliary canaliculi is an excretory route for hepatocyte lysosomes. To date, we have: 1) established valid assay conditions for 3 lysosomal hydrolases (beta-galactosidase, N-acetyl-beta-glucosaminidase, and beta-glucoronidase), 2 plasma membrane enzymes (5'-nucleotidase and alkaline phosphodiesterase 1) and a soluble enzyme (LDH) in rat bile and liver; 2) demonstrated that coordinate secretion of these 3 lysosomal hydrolases into rat bile occurs to a greater extent than enzymes known to be associated with mitochondria, endoplasmic reticulum and cell sap; 3) demonstrated a dissociation of bile flow, biliary lipid output, and biliary total protein output from biliary lysosomal enzyme secretion under non-cholestatic and cholestatic conditions; 4) demonstrated in hamsters that a non-cholestatic dose of ethynylestradiol increases hepatic lysosomal enzyme activity, an effect blocked by the anti-estrogen, clomiphene; 5) demonstrated that large molecular weight 3H-Triton WR-1339 purified by molecular sieve chromatography is both lysosomotropic for hepatocyte lysosomes and excreted into bile; 6) demonstrated that feeding, but not glucagon and Triton WR-1339, increases the output of lysosomal protein into bile; 7) successfully overload the livers of rats with iron and copper which markedly increased the biliary excretion of these two metals; and 8) initiated a collaborative study in the guinea pig exploring the role of gastric cell acid hydrolases in the pathogenesis of gastric ulcers and the relationship of gastric cell lysosomes to cytoprotection by prostaglandins.